Non-conductive and self-leveling leadframe clamp insert for wirebonding integrated circuits

ABSTRACT

A leadframe clamping apparatus includes a resilient polymeric membrane which permits self-leveling compensation of a variably movable clamp insert for variations in leadframe thickness. The clamp insert is formed of a polymer such as polyimide to provide further compensation for leadframe variations.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the manufacture of semiconductordevices. More particularly, the invention pertains to methods andapparatus for clamping portions of leadframes for making conductive wireconnections (wire bonds) between portions of the leadframe and the bondpads of the semiconductor device.

2. State of the Art

Semiconductor packages are formed in a variety of different designs.Among the various package configurations are dual in-Line packages(DIP), zig-zag inline packages (ZIP), small outline J-bends (SOJ),multi-level leads-on-chip (MLLOC), tape-under-frame (TUF), thinsmall-outline packages (TSOP), plastic leaded chip carriers (PLCC),small outline integrated circuit (SOIC), plastic quad flat pack (PQFP),thin quad flat pack (TQFP), and interdigitated leadframe (IDF).Wirebonding of each type of package requires a leadframe clamping devicewith particular dimensions and/or features.

In general, all package designs have several common elements. Theseinclude a sealed package enclosure, a die-attachment area, bonding wiresfor making electrical contact between the bond pads of the die and theleads of the package, and the inner and outer portions of lead fingersof the metal lead system of the package.

Typically, the leads of a leadframe for a semiconductor device are firstformed in multiple pattern units in a leadframe, a metal strip withmultiple bonding sites, each of which provides the leads for thepackaged device and, in some instances, may provide support for thesemiconductor device. A typical conventional leadframe strip is producedfrom metal sheet stock, such as a copper alloy, and has "paddles" uponwhich the semiconductor devices are mounted. During the wirebondingprocess the leadframe strip is moved and indexed from bonding site tobonding site through a clamping apparatus which retains the leadframestrip at sequential bonding sites for producing a plurality ofwire-bonded semiconductor devices. The typical conventional bondingmachine is designed with parallel non-resilient upper and lower clampingsurfaces.

The wirebonding process comprises attaching fine or small diameter wiresto bond pads on the semiconductor device and to portions of theleadfingers of the leadframe strip. The wirebonded semiconductor devicesare then further processed or encapsulated into packaged semiconductordevices.

As manufactured, leadframe strips typically vary in width, camber, andthickness. For example, a leadframe strip may vary in thickness fromedge to edge. Even small differences in thickness from one leadfingersto another may significantly affect the clamping effectiveness duringthe wire bonding process. Lead fingers which move during the wirebonding process may tend to be insufficiently bonded or have poor wirebonds, and, as a result, ultimately fail.

The result of such leadframe variations has been recognized for a longtime, and the patent literature shows various apparatus directed towardresolving the problem.

U.S. Pat. No. 4,765,531 of Ricketson et al. discloses a wirebondingworkstation with a planar upper clamp plate having a window.

U.S. Pat. No. 5,307,978 of Ricketson et al. discloses a leadframeclamping apparatus having an upper clamp plate with a window. This is aconventional clamp plate used on Kulicke and Soffa wirebonding machines.

U.S. Pat. No. 5,647,528 of Ball et al. and U.S. Pat. No. 5,197,652 ofYamazaki disclose dual leadframe clamping apparatus. Primary fixedclamps are augmented with a secondary independent clamp which moves withthe bonding apparatus from leadfinger to leadfinger. The independentclamp of Ball et al. may include insulation or cushioning on its end, orbe equipped with a spring, to control the compression force on theindividual leadfinger.

U.S. Pat. No. 3,566,207 of Adams discloses a clamping apparatus forholding a leadframe in place while an integrated circuit chip is bondedto a chip mounting pad. The clamping apparatus consists of a pair ofnarrow clamps, each of which is pressed downward on a leadfingers of theleadframe.

In U.S. Pat. No. 3,685,137 of Gardiner, multiple anvils are positionedover leadfingers to clamp them downwardly against a plunger.

U.S. Pat. No. 4,821,945 of Chase et al. describes a leadframe clampingapparatus, in which a clamp adjacent the wirebonding capillary clampsthe lead finger being wirebonded against movement.

For example, U.S. Pat. No. 5,035,034 of Cotney discloses a metal clampframe with a clamp insert. The insert includes a series of flexiblefingers, each of which is positioned to clamp one of the leadfingers onthe leadframe. The Cotney invention requires a separate clamp insert forevery device having a slightly different pattern, number or length ofleadfingers. Thus, each insert is very product-specific. Moreover, themanufacture of such a clamp insert wherein all of the flexible fingersprovide the same clamping force, even after extended use, is conceivablydifficult and expensive. The individual clamping fingers are fragile andeasy to distort. Weakening or breakage of a single flexible finger willrequire replacement and/or the fabrication of a completely new insert.

U.S. Pat. No. 5,322,207 of Fogal et al. describes a leadframe clamp withdual wirebonding windows for wirebonding two semiconductor dice at atime, i.e. without moving the leadframe. A heating block is configuredto simultaneously heat the paddle contact areas of both leadframe"frames".

While prior art clamping devices are acceptable, they suffer from acommon drawback, i.e., the inability to easily accommodate dimensionalvariations in the leadframe strip. Wirebond failures resulting from suchvariations are unacceptable in the current state of integrated circuit(IC) semiconductor device manufacture. A self-leveling clampingapparatus is needed which is inexpensive to construct, quickly adaptableto all leadframe sizes and types, permits rapid wire-bonding of theleads of the leadframe to the bond pads of the semiconductor device, andwhich significantly reduces damage to wirebonds and leads.

BRIEF SUMMARY OF THE INVENTION

The invention comprises an improvement in an apparatus for clamping asubstrate; e.g., leadframe to a wirebonding machine for performing anintegrated circuit wirebonding operation. In the invention, a polymericclamp insert with a wirebonding window and a clamping surface isinserted in a clamp holder. A thin resilient membrane is placed abovethe clamp insert. The clamp insert has sufficient "play" or latitude ofmovement so that the clamp insert is self-leveling or self-adjusting onthe leadframe upon application of a clamping force. The resilient memberensures that the clamp insert is nearly uniformly compressed downwardlyon the leadfingers about the die, irrespective of side-to-side orend-to-end thickness variations in the leadframe.

The resilient member also acts as a dampener to absorb mechanical shockswhich may otherwise damage the leadframe, die or bondwires.

The apparatus of the invention may be incorporated in a multi-memberself-levelling or self-adjusting insert member which is inserted into aclamp insert carrier. The insert member has a wirebonding windowsurrounded by a narrow clamping surface wherein compensation fornon-uniform leadframe thickness is provided. Preferably, the insertmember is formed of a polymer whereby additional advantages accrue fromboth the non-conductive electrical property, the low heat conductiveproperty of the insert device, and the degree of elasticity in thepolymeric leadframe insert itself. The insert member is configured toprovide the required compensation without permanent deformation.

In one form the clamp apparatus of the invention includes (a) a clampinsert holder with an insert aperture therethrough, (b) a clamp insertwith a bonding window and a clamping surface to contact the leadframe,(c) an elastic member formed of a polymeric material, e.g. apolytetrafluoroethylene material or a urethane material, and (d) aretaining member which retains the elastic member in a position biasedagainst the insert.

The insert has a generally peripheral clamping surface or ridge, and isformed of a non-conductive polymer having a low thermal conduction rate,such as a polyimide material, or other suitable type material. Theinsert is positioned in the insert aperture of a metal clamp insertcarrier and extends therethrough to provide a peripheral clampingsurface against the leadframe about a die adhered to a leadframe paddle.The insert and elastic member are held in place during clamping by aretainer, typically formed of a removable metal plate.

A variety of clamp inserts may be formed for differing semiconductordevice/leadframe configurations. Each clamp insert may be used forwirebonding different semiconductor devices, thus minimizing the numberof required inserts in a wirebonding operation. Thus, while the clampinserts may be considered as product specific, each insert may typicallyaccommodate a variety of package types or sizes. Moreover, the clampinserts are easily and quickly exchanged i.e. installed and removed, forwirebonding different packages with the same insert carrier.

Using a generic insert carrier applicable to a particular leadframewidth, inserts of various product-specific dimensions may be formed forwirebonding a wide variety of semiconductor packages including DIP, ZIP,TUF, SOJ, TSOP, PLCC, SOIC, PQFP, TQFP and IDF.

The thin member comprises a layer of a compressible elastic materialwhich acts as a dampener and a self-levelling or self-adjusting device.Upward forces exerted by the leadframe against the insert by non-uniformleadframe width, etc. are absorbed by the layer of elastic material,ensuring a generally uniform clamping force over the entire clampingsurface.

In addition, heat losses from the leadframe and die are much reduced bythe clamp insert which has a low heat conductivity.

Furthermore, the electrically non-conductive nature of the clamp insertavoids damage to the die, leadframe and wires due to accidentalelectrical discharge, e.g. shortcircuits.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated in the following figures, wherein theelements are not necessarily shown to scale.

FIG. 1 is a plan view of a prior art semiconductor leadframe strip;

FIG. 1A is an enlarged view of portion 1A of the leadframe strip of FIG.1;

FIG. 2 is an enlarged cross-sectional side view of a leadframe clampingapparatus of the invention;

FIG. 3 is an exploded isometric view of a leadframe clamping apparatusof the invention including a clamp insert, a clamp carrier, adampener/compensator layer and a retainer;

FIG. 4 is an isometric bottom view of a clamp insert of the invention;

FIG. 5 is a top view of a clamp insert of the invention;

FIG. 6 is a bottom view of a clamp insert of the invention;

FIG. 7 is a cross-sectional end view of a clamp insert of the invention,as taken along line 7--7 of FIG. 6;

FIG. 8 is a cross-sectional side view of a clamp insert of theinvention, as taken along line 8--8 of FIG. 5;

FIG. 9 is a cross-sectional side view through a flange of a clamp insertof the invention, as taken along line 9--9 of FIG. 5;

FIG. 10 is an exploded isometric view of another embodiment of aleadframe clamping apparatus of the invention including a clamp insert,a clamp insert carrier, a dampener/compensator layer and a retainerplate with lockbars; and

FIG. 11 is a bottom isometric view of a clamp insert insertable in theinsert carrier of FIG. 10.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

A representative metal leadframe strip 10 used in semiconductorintegrated circuit manufacture is shown in drawing FIG. 1. The leadframestrip 10 is a metallized design configured with several e.g. eight framesections 12, each frame section having a mounting paddle 14 for mountinga semiconductor device. The leadframe strip 10 includes parallel spacedstrip rails 16, 18 formed with a pattern of indexing openings 26 forhandling by automated machinery. The leadframe strip 10 includes withineach frame section 12 an array of leadfingers 22 adapted for attachmentto the bond pads of a semiconductor device 36, hereinafter referred toas a die or dice, during the wire bonding process. In general, theterminal ends 24 of the leadfingers 22 will become the external leads ofa completed semiconductor package. In the current technology, the metalthickness 62 (FIG. 2) of single-layer leadframe strips 10 is typicallyabout 20 to 40 μm but may be any thickness which permits accuratewirebonding and sufficient strength of the finished leads for theintended purpose.

In the manufacturing process, the leadframe strip 10 is typicallytreated as a unit from attachment of the dice to the paddles 14 up untilseparation of the individual frame sections 12 of the leadframe stripinto unit packaged semiconductor devices.

In the wirebonding apparatus and process as practiced with the presentinvention, a lower clamp member is a planar surface of e.g. awirebonding machine platform and/or block heater, and an upper clampmember e.g. clamp insert clamps a narrow peripheral portion 25 about thedie and adjacent leadfingers. The dimensions of the peripheral portion25 are configured to provide sufficient room for access of thewirebonding arm to the leadfingers and die, and immobilizing theleadfingers. The clamping apparatus is illustrated in detail in thefollowing figures and description.

Turning to drawing FIG. 2, a general representation of the leadframeclamping apparatus 28 of the invention is shown in cross-section. Forthe sake of illustration, the portions of the leadframe clampingapparatus 28 on each side of centerline 38 are mirror images of eachother.

A wirebonding platform 32 of a bonding machine is shown with a blockheater 34 for heating die 36 and leadfingers (leads) 22 of leadframestrip 10 for the wirebonding operation. The platform 32 generallycomprises a lower clamp member for holding the leadframe strip 10 whileconductive wires 48 are bonded to the leadframe and die 36. Theexemplary leadframe clamping apparatus 28 includes (in addition to theplatform 32) a clamp insert carrier 20, a clamp insert 30 which rides inthe carrier 20, a thin resilient member 40, and a clamp insert retainer50. The clamp insert carrier 20 is generally configured to clamp theopposing strip rails 16, 18 (not shown in FIG. 2) of the leadframe 10.An insert window 42 in the clamp insert carrier 20 is configured to holda clamp insert 30 which has a wirebonding window 44 with a lowerperipheral surface 46. The lower peripheral surface 46 comprises anupper clamping surface which engages the upper surface of the leadframe10 about the die 36 for wirebonding, the surface 46 corresponding toperipheral clamping surface 25 in drawing FIGS. 1 and 1A.

The clamp insert 30 and the overlying resilient member 40 are retainedin position in the insert carrier 20 by retainer 50 which may be e.g. ametal plate. As mounted, the retainer 50, resilient member 40 and insert30 have coaxial threaded holes 56 through which threaded fasteners 60,such as screws, are threaded into threaded holes 58 along axes 65 in theinsert carrier 20. As mounted, the insert 30 is capable of tilting aslight degree in any direction within the insert carrier 20 tocompensate for variations in the thickness 62 of the leadframe strip 10.

Upon completion of wirebonding a frame section 12, the clampingapparatus 28 including the insert carrier 20, insert 30, resilientmember 40 and retainer 50 are lifted from the leadframe strip 10 and thestrip advanced to the next frame section.

For a typical insert 30, the width 52 (FIG. 1) of the lower peripheralsurface 46 may vary from about 0.01 to about 0.08 inches (0.254 to 2.032mm). Thus, an exemplary insert 30 having a rectangular wirebondingwindow with uniform inner dimensions of 0.25 by 0.45 inches (0.635 by1.143 cm.) will have a total clamping area of approximately 0.0144 to0.1376 square inches (0.0929 to 0.8877 square cm.). Although width 52may be as much as 0.08 inch (2.032 mm) or more, a more preferred rangeof widths is between about 0.02 and 0.04 inches (0.508 and 1.016 mm), atwhich the clamping area of the lower peripheral area is between about0.0264 and 0.0528 square inches (0.17 and 0.34 square cm).

The preferred insert clamping pressure 102 on a typical frame section bythis exemplary insert 30 is variable but, typically is in the range ofabout twenty (20) to about thirty (30) psi.

The total compressible surface area of the resilient member 40 willtypically be much larger than the area of the lower peripheral surface46 of the insert 30. For example, an insert 30 of the above example mayhave a resilient member compressible area of about 0.50 square inches(3.23 square cm), about 10-20 times the area of lower peripheral surface46. The area of the resilient member 40 may be varied to provide thedesired compensation for leadframe variations, depending upon thestress-strain relationship and thickness 54 of the resilient member 40.Thus, the force necessary to achieve a desired compensation may becalculated and enabled by using a resilient member 40 of a particularmaterial, thickness 54 and area. Typically, the thickness 54 of theresilient member 40 is in the range of about 0.005 to 0.1 inches (0.0125to 0.25 cm.). Members 40 of differing clamping areas may be provided fora particular insert carrier 20, and selectable for inserts withparticular window sizes and clamping areas. The members 40 may bequickly and easily interchanged, for example, by removing four screwfasteners.

As an example, a clamping apparatus 28 of the invention may beconfigured for a maximum dimensional compensation (insert movement ortilting) of about 0.0002 to 0.02 inches (0.0005 to 0.05 cm.). Thecompensation movement is to be absorbed by a resilient member 40 ofabout 0.005 to 0.1 inch (0.0125 to 0.25 cm.) thickness.

The clamping insert 30 has an enlarged upper portion 70 in which thewirebonding window 44 has expanded dimensions for accommodating thebonding machine head, not shown. The clearances 66, 68 between the outerwall surfaces 64 of the insert 30 and the insert window 42 of the insertcarrier 20 are configured to provide a desired tiltability of the insert30.

The clamping insert 30 is preferably formed of a polymeric material suchas polyimide. Vespel polyimide material, a trademarked material producedby DuPont, has been found to be very suitable, although other polymerswith similar mechanical, electrical and heat conduction properties maybe used.

Exemplary embodiments of the present invention for use on a Kulicke &Soffa Industries model 1484 wirebonding machine are depicted in drawingFIGS. 3 through 11. Other suitable wirebonding machines are commerciallyavailable from a variety of manufacturers, including (in addition to K &S), Shinkawa, Kiajo Denki, and ESEC.

In the remaining drawing FIGS. 3 through 11, the leadframe strip 10 isnot illustrated or pictured, but it is understood that the wirebondingclamp apparatus 28 is for clamping a leadframe strip to an underlyingwirebond machine platform, with a bonding site of the leadframe stripi.e. die and leadfingers accessible through the wirebonding window ofthe clamp insert 30.

As depicted in drawing FIG. 3, a clamping apparatus 28 of the inventionfor wirebonding LOC and SOJ devices uses an insert carrier 20 with holes72 for mounting leaf spring members 74. Such leaf spring members 74 aredownwardly biased and push the leadframe strip 10 away from the clampinsert carrier 20 and insert 30 when the carrier is lifted for movingthe leadframe strip. The leaf spring members 74 are disclosed in U.S.Pat. No. 5,322,207, commonly assigned to the assignee of the presentinvention. As described in that publication, the insert carrier 20 alsohas holes 78 and 80 for aligning the carrier with the lower clamp member(not shown), the upper compression force driver (not shown), and theleadframe strip 10.

The surface 43 of insert window 42 of the carrier 20 is shown withsubsurface stages 76 upon which the clamp insert 30 is mounted bythreaded fasteners 60 seated in threaded holes 58. When fully seated andat its lowermost position in the insert window 42, the lower peripheralsurface 46 (see drawing FIGS. 4, 6) of width 52 is below the lowersurface 82 of the carrier 20 and biased downwardly by the retainer 50and intervening resilient dampening/compensating/adjusting/aligningmember 40. The exemplary insert window 42 is shown with sloping walls84. The insert carrier 20, clamping insert 30, member 40 and retainer 50are joined and held together by threaded fasteners 60 threaded intoholes 58 along axes 65 in the insert carrier. The threaded fasteners 60are fastened to the carrier 20 such that the insert 30 may be pushedupwardly against the resilient member 40, which resists upward movementof the insert but permits a slightly tilted or canted engagement of theinsert against it. Thus, the resilient member 40 permits self-levelingof the clamp insert 30 to compensate for non-uniformity of leadframethickness 62.

The embodiment of polymeric clamp insert 30 shown in drawing FIGS. 3through 9 is particularly configured for wirebonding a leads-on-chip(LOC) semiconductor package with small-outline J-bends (SOJ). The clampinsert 30 has a mounting flange 86 and a window frame 88 which isperipheral to the wirebonding window 44 and extends downwardly to alowermost window opening 44A. The inner walls 90 of the window frame 88may be sloped from a relatively large upper window opening 44B at angle94 as shown to provide working room for the automated wirebonder tooperate. The inner walls 90 are dimensioned and shaped to achieveoperating room for wirebonding a device requiring a particular sizedlowermost window opening 44A. The general dimensions of the lowermostwindow opening 44A are shown as width 96 and length 98. The flange 86may include alignment holes 92 to accurately position the insert 30within the insert carrier 20. The outer wall surfaces 64 of the clampinginsert 30 may be partially sloped, such as at angle 100.

As depicted in drawing FIG. 3, the resilient member 40 is a thin memberof e.g. polytetrafluoroethylene or urethane which has a window 44C whichgenerally is about equivalent to window 44B in dimensions. The resilientmember 40 may be stamped or cut to the desired dimensions for placementatop the clamping insert 30. The resilient member 40 is shown withthreaded holes 56 for passage of threaded fasteners 60. The preferredmaterials of construction have a coefficient of compression of betweenabout fourteen (14) and about 35 mpA @ 1% of strain and a permanentdeformation point which is sufficiently high to be unattained in thisapplication. As already noted, the thickness 54 of the resilient member40 is between about 0.005 and about 0.1 inch (0.0125 and 0.25 cm),depending upon its mechanical properties, expected variation inleadframe thickness 62, clamping pressure, and configuration of theclamping insert 30.

The retainer 50 is shown as a flat plate with window 44D and threadedholes 56 which generally match those of the resilient member 40.

Referring to drawing FIG. 10, another embodiment of the invention isdepicted as using a "universal" clamp insert carrier 20 having a shapesimilar to that disclosed in U.S. Pat. No. 5,307,978. In that reference,the insert carrier 20 has a simple window merely comprising a hole, andis held immobile by a clamp frame member at each end of the carrier. Theunderlying leadframe strip 10 is movable in x, y, z and theta directionsfor positioning during wirebonding.

As shown in drawing FIG. 10, the clamp insert carrier 20, as modified inaccordance with the invention, comprises flat plate portions 110, eachwith an upturned flanged end 112. The flanged ends 112 are fixed to thebase of a work station, not shown, by e.g. threaded fasteners passedthrough apertures 114. Additional apertures 116 may be provided foralignment of the insert carrier 20 with the underlying platform andleadframe strip, not shown in this figure.

A centrally located insert window 120 is sited between two endframemembers 118. A generally horizontal matte portion 122 limits downwardmovement of a clamping insert 30 and defines the lowermost open windowportion 126 of the insert window 120.

The clamping insert 30 (see FIGS. 10 and 11) is a simple window framewith wirebonding window 134, and fits into the insert window 120. Theinsert 30 has a flange portion 124 which mounts on the matte portion122, and a lower peripheral portion 128 which extends downwardly throughthe lowermost window portion 126 of the insert window 120 of the carrier20, to be below the lower surface 130 of the carrier. As in theembodiment already described herein, the bottom surface 132 of the lowerperipheral portion 128 engages and clamps downwardly on the leadframestrip about the die and leadfinger ends of a frame section. The lowerperipheral portion 128 of the insert 30 is shown with slots 136, whosepurpose is to provide clearance for the tie bars connecting the diepaddle to other portions of the leadframe that are not clamped duringthe wire bonding operations. The insert window 120 and insert 30 areconfigured to have a limited degree of linear vertical and tiltingmotion, so that the bottom surface 132 comprising an upper clamp may beself-leveling or self-adjusting on the leadframe.

As already indicated, the insert 30 is preferably formed of a polymericmaterial such as polyimide.

While the exemplary insert 30 shown in drawing FIGS. 10 and 11 isdesigned for wirebonding of a thin-quad-flat-pack (TQFP) device, thewindow may be shaped and sized to accommodate any other packagingdesigns and sizes, including those with multi-level leads. Thewirebonding window 134 may be of any shape and size for wirebonding aparticular die-leadframe combination. Thus, the wirebonding window 134may be round or octagonal, for example.

The resilient member 40 is formed of a thin sheet of material, e.g.polytetrafluoroethylene material or urethane material, in which window138 is formed. The member 40 absorbs upwardly directed forces of theinsert 30 as a clamping force is applied. The resistance of member 40may be varied by varying its thickness and planar surface area, and/orusing a different material.

The retainer 50 is depicted as a cover plate with turned-down ends 142with tabs 144, and a window 140 in its horizontal surface 146. Theretainer 50 holds the clamping insert 30 in the insert window 120 andholds the resilient member 40 atop the retainer. As shown, each of twolock bars 104 has a lower indent 146 into which a retainer tab 144 fits.The lock bars 104 are placed over the two retainer tabs 144 and attachedby suitable threaded fasteners, not shown, through holes 152 and alongaxes 148 into threaded holes 150.

As shown in drawing FIG. 10, the insert 30, member 40 and retainer 50are formed without any threaded holes, thus simplifying theirconstruction.

The leadframe clamping apparatus 28 may be advantageously used forwirebonding a tape-under-frame (TUF) device configuration. In TUF, thelead pattern is formed on a tape. During wirebonding, the tape, ratherthan the metal lead pattern, is directly exposed to the heating block.The variation in thickness of the leadframe-tape combination often makeseffective clamping difficult. The selfleveling or self-adjusting featureof the clamping apparatus 28 overcomes this problem.

There are numerous advantages to the clamping apparatus 28 as describedherein. First, movement of leadfingers during wirebonding is avoided,enabling more uniform and precise bonding. In addition, heat lossesthrough the clamping apparatus are reduced because of the low heattransfer of the insert. Consistent bonding temperatures are achievedacross all leads of the leadframe strip. Thus, the rate of wirebondrejection may be significantly decreased.

Clamping inserts 30 may be quickly and cheaply made of polymericmaterial without grinding, polishing or heat treatment. They may beformed in a variety of designs and dimensions for every type and size ofpackage which is to be made. The inserts 30 may be easily and quicklyinterchanged without distorting a tool setup. Where the heating blockdoes not need to be interchanged, for example, in converting from a LOCto a TUF device, conversion is very quick.

Interchangeable resilient members 40 may be punched out of inexpensivesheet material to achieve any desired correction of dimensionalvariation in a leadframe. A minimum of storage space is required forstoring a supply of replacement members 40 and inserts 30 in all usefulstyles/sizes/materials.

The insert 30 and resilient member 40 may be used repeatedly withoutdamage because, in use, the permanent deformation pressure is neverattained.

The net result of using the apparatus is a reduction in time from thedesign stage to commercial production. Furthermore, the tooling costsmay be much decreased. In addition, the rejection rate is decreased,resulting in greater profitability.

Preliminary tests have shown an improvement in bond pull and sheartests, and lower rejection rates than is otherwise achieved.

It is apparent to those skilled in the art that various changes,additions and modifications may be made in the improved leadframeclamping apparatus as disclosed herein without departing from the spiritand scope of the invention as defined in the following claims.

What is claimed is:
 1. A method of adjusting clamping apparatus in a leadframe clamp, said method comprising the steps of:providing a lower clamping surface for supporting a leadframe strip; providing an upper clamping member comprising a wirebonding window frame having a window therein adapted to move under a clamping force to engage portions of said leadframe strip underlying said window frame; providing a resilient member located substantially above said upper clamping member; and compressing said upper clamping member to substantially cause said window frame to engage said portions of said leadframe strip underlying said window frame.
 2. The method of adjusting of claim 1, wherein said upper clamping member is formed of a polymeric material.
 3. The method of adjusting of claim 1, wherein said upper clamping member is formed of a polyimide material.
 4. The method of adjusting of claim 1, wherein said resilient member comprises a polymeric material.
 5. The method of adjusting of claim 1, wherein said resilient member comprises one of polytetrafluoroethylene and urethane.
 6. The method of adjusting of claim 1, wherein a thickness of said resilient member is approximately 0.005 to approximately 0.1 inches (approximately 0.0125 to 0.25 cm).
 7. A method of adjusting clamping apparatus in a leadframe clamp used in electrically connecting a semiconductor device to a leadframe, said method comprising the steps of:providing a lower clamping surface for supporting a leadframe strip; providing an upper clamping member comprising a wirebonding window frame having a window therein adapted to move under a clamping force to engage portions of said leadframe strip underlying said window frame; providing a resilient member located substantially above said upper clamping member; and compressing said upper clamping member to substantially cause said window frame to engage said portions of said leadframe strip underlying said window frame.
 8. The method of adjusting of claim 7, further comprising the steps of:providing a semiconductor device connected to said leadframe strip; and electrically connecting portions of said leadframe strip to portions of said semiconductor device.
 9. The method of adjusting of claim 7, wherein said upper clamping member is formed of a polymeric material.
 10. The method of clamping of claim 7, wherein said upper clamping member is formed of a polyimide material.
 11. The method of adjusting of claim 7, wherein said resilient member comprises a polymeric material.
 12. The method of adjusting of claim 7, wherein said resilient member comprises one of polytetrafluoroethylene and urethane.
 13. The method of adjusting of claim 7, wherein a thickness of said resilient member is approximately 0.005 to approximately 0.1 inches (approximately 0.0125 to 0.25 cm). 